Tractor trailer fuel transport tanks and fuel storage tanks in general employ pressure relief valves for preventing overpressurization of the tank, particularly when employing an inert gas under light pressure to purge oxygen from an empty tank and prior to filling of the same with a liquid hydrocarbon fuel. The presence of significant oxygen content within the tanks at the time of filling of the tank with the liquid hydrocarbon fuels significantly increases the possibility of an explosion occurring, particularly where, due to the chemical makeup of the fuel or other combustible liquid being carried by the tank, there is a buildup of static electricity capable of igniting the fuel or like liquid during filling of same. Typical trailer fuel transport tanks formed of stainless steel plate are rated for 25 psi. In contrast, the aluminum trailers which have come into vogue such as those referred to as MC306 carry a rating of 3 psi. While the aluminum trailer tanks carry the liquid hydrocarbon at atmospheric pressure, in order to purge the aluminum trailer tanks with an inert gas such as nitrogen, to reduce oxygen content substantially below 9%, with below 7% being preferred and below 5% being most preferred (all contents by volume), with the oxygen escaping the interior of the aluminum trailer tanks via one or more vapor recovery units within the tank wall, there is a high potential for potential damage to the trailer should the tank become pressurized. Whether such trailer transport tanks are of stainless steel or aluminum, the tanks carry pressure relief valves to prevent overpressurization. While most trailers are equipped with a vapor recovery system which includes means for relieving the pressure and preventing overpressurization of the trailer transport tank, such pressure relief vapor recovery system often fails. Where the trailer transport tank or the like is formed of aluminum, it imperative that while purging of the tank with an inert gas such as nitrogen, the tank pressure be relieved at 1.5 psi or near that value.
Therefore, it is a primary object of this invention to provide a nitrogen distribution nozzle for effectively diffusing the nitrogen gas under pressure throughout an aluminum trailer transport tank or the like, which performs a pressure relief function as low as 1.5 psi, which is of simplified structure, which is projected within a tank inlet aperture and gravity maintained therein; and which is physically raised under gas pressurization of the tank during nitrogen purging to prevent overpressurization of the tank during purging to self pressure relieve, which is of low cost and which is highly reliable.